(1) Field of the Invention
This invention relates to hermetically sealed pouches and more particularly to a pouch constructed of a multi-ply laminate for use in packaging snack food products.
(2) Description of the Prior Art
Packages constructed from flexible materials such as laminates are well known. Various products have been placed in hermetically sealed pouches to preserve their freshness and opening means have been provided for gaining access to the pouch interior. This is shown, for example, in U.S. Pat. No. 3,559,800, which issued to John Parkman Butler on Feb 2, 1971, in connection with a pouch made from a laminate wherein the inner ply is adhered to the outer ply only in selected locations and a line of weakness is impressed in the inner ply for ease in opening the pouch. Pouches made from fully laminated plies are, of course, also well known and have been provided with opening devices of various sorts, as illustrated in U.S. Pat. No. 3,426,959, which issued to Jerome H. Lemelson on Feb. 11, 1969, and wherein a tear opening is defined by a line portion of the wall of the package, such line portion being of reduced thickness and having means disposed therealong for effecting a controlled separation along the line portion. In one embodiment the use of a pair of thinned, parallel lines of weakness on the sides of a tearstrip is disclosed U.S. Pat. No. 3,186,628, issued to William A. Rohde on June 1, 1965, also concerns a package formed of a flexible packaging material. The packaging material comprises a thermoplastic film having formed therein an imperforate continuous, or substantially continuous, groove line which is relatively thinner than the remaining body portion of the film and which provides a means by which a wall of the package may be ruptured for access to the package contents. The thermoplastic film can be employed alone or supported by lamination to other films or sheet material. Various means can be used to form the groove line; for example, the Rohde patent suggests probes projecting into the path of the thermoplastic film as it is being extruded or, alternatively, using an electrically or otherwise heated bar. The prior art also illustrates other more sophisticated ways in which similar line of weakness can be formed. One such disclosure is made in U.S. Pat. No. 3,909,582, which issued to William Edmund Bowen on Sept. 30, 1975, wherein a laser beam is used to score (i.e. provide a thinned groove in) a layer of plastic film in a multilayer laminate. The score line functions as a line of weakness along which the laminate can be torn and, thus, functions as a package opening device. With respect to tear initiating means, such is generally old in the art, others having used notches or slits for such function.